The present invention is related to the Broadband Network system as described in the technical requirements document, TR-101 (from Broadband Forum). The current version of the TR-101 document focuses on IPv4 and it is currently being extended with IPv6 functionality (WT-177).
A basic principle of the TR-101 is the ability for the Access Network (AN) to insert a DSL port-related identity into messages sent toward the Broadband Network in order for the Broadband Network Gateway (BNG) to identify the configuration associated with that end-user on that port. Thus when an end-user requests an IP-address, and the end-user uses IPoE (as opposed to IPoPPP), the Dynamic Host Configuration Protocol (DHCP) relay agent in the access network inserts an “option 82” (with the port identity) into the DHCP request before forwarding it upstream. This enables the BNG's DHCP server to uniquely identify the end-user/port/circuit (as also specified in RFC3046) related to the DHCP request.
In IPv6, the IP address can be dynamically assigned by one of two methods: either DHCPv6 or the Neighbor Discovery (ND) protocol (as specified in RFC4861). The DHCPv6 method is handled in a manner similar to IPv4, using a DHCPv6 parameter to hold the port identification. The ND method, however, poses a problem because the current specification does not offer any parameter/attribute where the port identification can be inserted.
Some, if not most, current commercially available broadband access devices do not offer a DHCPv6 client; they only support ND. An example of such a device is the popular PC operating system, Windows XP. When such a PC is connected to a broadband network via a residential gateway such as a bridged Customer Premises Equipment (CPE), the PC initiates ND signaling with an ND Router Solicitation (RS) message and is expecting to receive an IP address via an ND Router Advertisement (RA) message in return. However, the BNG cannot identify which port the request came from and cannot associate a certain policy with the IP address assignment (for example, limiting the number of simultaneously assigned addresses for that user). Therefore, the discovery process fails. The problem is not limited to PCs, but also applies to any user equipment (routing CPE or any device behind a bridged CPE) that uses ND for IPv6 address configuration.